The spread of mobile devices such as mobile handsets, media players, tablet computers and laptops/notebooks/netbooks and ultra-books increases user demand for access to wireless power points at which they may transfer power to charge mobile devices while out and about or on the move.
Wireless power transfer systems supporting such requirements are known, such as the system described in United States Patent Application 2012/0193993 A1, to Azancot “ENERGY EFFICIENT INDUCTIVE POWER TRANSMISSION SYSTEM AND METHOD”, which is incorporated herein by reference. The system includes an inductive power transmitter and an inductive power receiver, which are provided to form an inductive couple allowing energy to be transferred from a power supply to an electric load associated with an electronic device without a wired connection therebetween. The inductive power transmitter may further adjust the amount of energy being transmitted to the power receiver and respond to communication signals from the inductive power receiver which is aligned thereto.
Inductive power coupling allows energy to be transferred from a power supply to an electric load without a wired connection therebetween. An oscillating electric potential is applied across a primary inductor. This sets up an oscillating magnetic field in the vicinity of the primary inductor. The oscillating magnetic field may induce a secondary oscillating electrical potential in a secondary inductive coil placed close to the primary inductive coil. In this way, electrical energy may be transmitted from the primary inductive coil to the secondary inductive coil by electromagnetic induction without a conductive connection between the inductors.
When electrical energy is transferred from a primary inductive coil to a secondary inductive, the inductors are said to be inductively coupled. An electric load wired in series with such a secondary inductive coil may draw energy from the power source wired to the primary inductive coil when the secondary inductive coil is inductively coupled thereto.
The strength of the induced voltage in the secondary inductive coil varies according to the oscillating frequency of the electrical potential provided to the primary inductive coil. The induced voltage is strongest when the oscillating frequency equals the resonant frequency of the system. The resonant frequency fR depends upon the inductance L and the capacitance C of the system according to the equation
      f    R    =            1              2        ⁢        π        ⁢                  LC                      .  
There is a need for an energy efficient inductive power transfer system which may extend the operational range of an inductive power outlet when the inductive power receiver is not exactly aligned thereto. The current disclosure addresses this need.